The present invention relates to a marking station for timber. More particularly, it relates to such a marking station which is used for defect locations and quality limits in timber and provided with a transporting device, a device for changing a transporting speed of the timber, and an indicating station part with a laser transmitter element for indicating first and second separating planes before and after a defect location and quality limits with a laser beam. The laser transmitter element can be moved by an operator along a guiding device parallel to the movement direction to indicating positions corresponding to the separating plane and the quality limits, and the indicating positions of the laser transmitter element are supplied to a computer for controlling in some cases an optimizing saw.
Marking stations of the above mentioned general type are known in the art. One of such marking stations is operative for stopping the timber upon recognition of a location to be indicated. It has been shown on Hannover Fair Ligna 1987 between May 27, 1987, and June 2, 1987, by the company Wadkin Leicester, Green Lane Works, Leicester LE5 4PF, England. The laser transmitter element is here the laser itself, and it is moved by the operator along the timber with a rope system to the respective indicating position. Because of the high mass of the laser transmitter element, it is quite difficult and relatively slow. Also, the constant holding of the timber for indicating makes the operation longer in an undesirable manner.
Another marking station is disclosed in the German document DE-GM 8,704,684.9. Here a laser 4 is arranged above the timber 3 and the operator 10 is located laterally of the timber. The laser sends a flat beam fan 9 perpendicularly to the transporting direction 11. The beam fan 9 shows on the timber 3 the separating plane with a light band 7 directly on the upper and front side and is reflected onto the lower and rear side through an inspection mirror 5. The inspection mirror 5 is arranged in an inclined manner near and under the timber 3 relative to the horizontal plane so that its normal 6 is directed toward the laser 4. The timber 3 is brought by the operator through a system of light barriers 19 and 21 to a standstill and then displaced manually to the respective indicating position. There an indicating signal is produced and supplied to a computer which is activated by measuring wheels 12, 16 and controls for example a cross-cut saw. The structural expenses are very high. The positioning of the timber 3 manually is time consuming. There is the danger that the eyes 10 of the operator can be hit by the laser beam 9 reflected from the inspection mirror 5.
A further marking station is disclosed in the German reference DE-OS 2,807,670. Here the timber 2 is transported transversely through an inspection zone 10. A stationary laser 26 sends a laser fan 27 onto a mirror 23 which is turnable above the inspection zone 10 about an axis 24 extending parallel to the movement direction of the timber 2. Through a follow-up control 22 the mirror 23 follows the turning of a handle 18 on an operator chair 13. The whole inspection zone 10 including the timber 2 located in it, is run over with the reflected laser fan 27 by actuation of the handle 18. A laser band 29 shows a separating plane whose position is introduced via a pushbutton 33 on the handle 18 as signal through a conductor 32 into the electronic circuit 31. The structural expenses here are also very high. The accuracy of the position detection is low because of the high turning ratio of the laser fan 27 because of the non-constant and great distance of the operator from the individual longitudinal regions of the timber 2.
The German document DE-OS 3,116,253 discloses a measuring system for example for a vehicle 1. A measuring bar 8, 21, 25 extends laterally parallel to the longitudinal axis of the vehicle 1, and a laser 10, 28, 30 is stationarily arranged on its one end. The laser sends a bundled laser beam parallel to the measuring bar. A part of the laser beam is deviated perpendicularly through a first deviating unit 12, 26, 34 in the direction of the vehicle 1. The remaining portion of the laser beam passes through the first deviating unit. This remaining portion can be deviated by a stationary second deviating unit 13 on the other end of the measuring bar 8 about 90.degree. along a further measuring bar 9, and there deviated by a third deviating unit 14 again by 90.degree. in direction of the vehicle 1 as shown in FIG. 1. The remaining portion of the laser beam can also be deviated in a fourth deviating unit 27, 35 on the first measuring bar 21, 25 in direction of the vehicle 1 as shown in FIGS. 2 and 3. The deviating units with the exception of the stationary second unit 13, are displaceable by the operator 15 manually or by a motor along their measuring bars and have a detector 40, 41 for markings 42 on the measuring bar. The detector detects the actual value of each measuring position of its deviating unit and performs the comparison with a nominal value for the associated measuring point 2-7 of the vehicle 1.
The German reference DE-OS 2,654,872 discloses a system of searching and optimizing for example for timber. A stationary laser 30 sends a laser beam in a beam separator 32, and its both output beams are deviated on surfaces of a rotatable polygonal mirror 34 and then on several mirrors 36, 38 and 40, 42, 44. Each output beam scans finally a surface of the timber 10 over an angle 46, 48 in a reciprocating manner. Two photodetectors 50, 52 and 54, 56 are directed to each surface and supply the sensing signals in an electronic evaluating circuit for automatically recognizing defect locations in the timber. This system requires high structural and circuitry expenses.
The German reference DE-PS 3,208,042 shows a system for testing of running material, especially a paper web 18, as to non-directional longitudinal and transverse defects 13 and 14. Here a laser beam from a stationary laser 1 is extended, subdivided and stretched until parallel partial beams 23 strike on a fast rotating polygonal mirror 8. The partial beams 23 are reflected on the material web 18 and form on it flying light points along the transversely extending testing line 27. The beams 24 reflected from the material web are received by a photoelectric converter 16 and converted into signals which are evaluated in an evaluating stage 17.